The present invention relates to a plastic magnet injection molding machine.
In the case of injection molding an anisotropic plastic magnet, a magnetic field has to be applied in the molding process. The conventional plastic magnet injection molding machines can be classified into two types according to the methods used to apply magnetic fields. That is, one is a type in which an exciting coil for producing a magnetic field is incorporated within a mold and the other is a type in which an exciting coil is arranged at the outer circumference of each of a stationary and a movable platen of a mold tightening device.
There are disadvantages in the type incorporating the exciting coil within the mold. That is, in order to incorporate the exciting coil into the mold, a space is necessary, so that the mold becomes correspondingly large, and it becomes necessary to use a large sized injection molding machine. In the case of a mold for simultaneously molding a number of products, the yield is reduced and the producibility is lowered.
On the other hand, in the type surrounding the stationary and movable platens with exciting coils, there are disadvantages as follows. That is, since the exciting coils are arranged respectively at the outer circumferences of the stationary and movable platens, the device becomes complicated and large in size. Besides, it has been necessary to remove the exciting coil every cycle whenever the molded products are taken out, so that it has been difficult to improve the efficiency in production.